Evidence of sexuality in induced tetraploids of Brachiaria brizantha (Poaceae)

Difficulties in obtaining new breeding lines of Brachiaria (Trin.) Griseb., an important forage grass in Brazil, are mostly related to differences in ploidy among the accessions, and to apomixis, an asexual mode of reproduction. Usually, sexual accessions are diploid while apomicts are polyploid. Induced tetraploids of Brachiaria brizantha (A. Rich.) Stapf have been successfully obtained and this paper presents the results of a study of their reproductive modes and fertility. Despite frequent meiotic aberrations during microspore development, the induced tetraploids produced viable pollen and produced progeny after controlled self-pollination. Similarly to the original diploid sexual progenitor, embryo sacs of the Polygonum type with confirmed meiotic origin were present in the induced tetraploids suggesting chromosome doubling did not alter the reproductive mode. The embryo sac of the Polygonum type was also observed in progenies obtained after self and open pollination. Nevertheless, embryo sacs of the Polygonum and the Panicum types within the same ovule were observed in some progenies obtained after open pollination, probably having resulted from hybridization with tetraploid, apomictic plants. Indeed, the compatibility of the progeny with tetraploid, apomictic B. brizantha was confirmed by the formation of mature caryopses after controlled pollination. Evidence is presented that the induced tetraploids and their progeny are sexual plants and that they are compatible with natural tetraploid B. brizantha. The induced tetraploids will be useful for analyses of apomictic inheritance as well as in the development of sexual tetraploid lines in Brachiaria breeding programs.     

In vitro induction of tetraploids in colchicine-treated cocoyam plantlets

A self-compatible (SC) variant of a wild diploid potato species, Solanum chacoense, which is normally self-incompatible (SI), was investigated for the nature and genetics of self-compatibility. It was crossed with a SI cultivated diploid potato species, S. phureja. The F₁ progeny segregated SC vs. SI. Diallel crosses were made among 15 F₁'s. Self-compatibility was tested in a selfed family of a parental SC variant and in sib-mated and selfed families of F₁ progeny. All the data suggest that there is a single dominant gene (Sli) with sporophytic action inhibiting S gene expression in the pollen. Plants having a ‘Sli’ gene, produce pollen which is compatible to its own parent and plants with similar S genes. The ‘Sli’ gene has been maintained in a heterozygous condition through eight selfing generations (S₈) implying that dominant homozygotes might be associated with lethality. This revised version was published online in July 2006 with corrections to the Cover Date.     

In vitro induction of tetraploids in Phlox subulata L.

Tetraploid plants of Phlox subulata L. were induced successfully by treating shoot tips in vitro with colchicine. Shoot tips excised from in vitro shoots were treated with four different concentrations of colchicine (0.005, 0.01, 0.02, 0.04%) in solid MS medium supplemented with 4.54 μM TDZ and 0.49 μM IBA for 10, 20 or 30 days, respectively. The survival rates of shoots tips were affected by the concentration of colchicine and the duration of treatment. High concentration and longer duration reduced survival of the shoot tips, but the effect of duration of colchicine was more than that of concentration. Tetraploid plants were obtained in all of the treatments, but the percentages of tetraploids varied among different treatments, from 25.0% to 75.0%. The most efficient condition for inducing tetraploids was to treat shoot tips with 0.005% colchicine for 20 days, with 30.0% survival rate of shoot tips and 6 tetraploid plants out of 10 plants examined. The rooted tetraploid plants were transplanted successfully in a solar greenhouse. Under the same growing condition, significant varieties in flower bud and flower sizes were detected between 2x and 4x plants. The flower diameters of tetraploid and diploid plants were 2.91 cm and 2.24 cm, respectively.     

Agronomic evaluation of AABB wheat tetraploids extracted from wheat neo-allohexaploids

In order to understand if the mechanisms leading to stabilization of hexaploid wheats occurred in early generations after hybridization or accumulated slowly over the evolutionary course, we extracted tetraploids from newly synthesized allohexaploid wheats and characterized the effects of changes in polyploidy levels. Extracted wheat tetraploids (ETW) were developed from two neo-allohexaploids and their five phenotypic traits were compared to the parents. The ETWs displayed few small amplitude differences relative to the tetraploid parent of the synthetics. This suggest that genomic changes that might have occurred during the first three generations of the newly-synthesized wheat allopolyploids had very weak effects on the phenotypes.     

耐盐芦笋引进品种筛选试验

通过对从美国特拉华洲引进 4个耐盐芦笋品种其耐盐性和产量的研究,筛选出适合黄河三角洲盐渍土地区生长的耐盐优质芦笋品种.结果表明:耐盐 2号、耐盐 4号 2个品种表现突出,各生育指标、耐盐性和产量均明显高于对照.     

Development of interspecific somatic hybrid cell lines in cultivated jute and their early characterization using jute chloroplast RFLP marker

A strong sexual incompatibility barrier that exists between the two cultivated jute species, Corchorus capsularis and Corchorus olitorius, limits the scope for improvement through genetic introgression. Protoplast fusion was carried out to generate interspecific hybrid cell lines. Cotyledonary cell protoplasts of C. capsularis and anthocyaninpigmented hypocotyl protoplasts of C. olitorius were used in the fusion experiments, which appeared to be visually useful in the early selection of the fused products. A chloroplast DNA (cpDNA) marker was developed in jute, which showed species‐specific hybridization patterns with EcoRI‐digested total genomic DNA of C. capsularis and C. olitorius. This cpDNA marker was used in the characterization of the somatic hybrid cell lines at their early stages of growth. Evidence for the presence of both types of cpDNA in the hybrid cell lines was obtained when the total genomic DNA of 4‐ to 7‐month‐old hybrid cell lines was challenged with the chloroplast DNA marker through Southern analysis. It was shown that the early segregation of the parental chloroplasts did not occur in jute, although this is common in other plant species. The hybrid nature of the fused cell lines could also be identified through peroxidase isozyme analysis. Isozyme banding patterns were complex and varied among the hybrid cell lines.     

Fertility improvement in autotetraploid sorghum. 3. Yields of cultivated tetraploids

Summary The development of tetraploid grain sorghum as a crop plant continues to show promise. Yields from bulk populations and lines withdrawn from such populations are now approaching levels realised by good diploid varieties. It seems that tetraploid grain sorghum populations in which high levels of recombination are attained by the use of the genetic male-sterile ms ₃, should respond profitably to the application of recurrent selection.Seconded from the Plant Breeding Institute, Trumpington, Cambridge.     

中国黄麻炭疽病病原菌的分离鉴定及系统发育分析

炭疽病是严重影响黄麻纤维产量和品质的主要真菌性病害,明确炭疽病病原菌种类并测定其致病力有助于黄麻抗病育种和优异抗病基因资源挖掘。本研究从福建省福州市、福建省漳州市、河南省信阳市、安徽省六安市、浙江省杭州市、广西省南宁市和湖南省长沙市等7个黄麻生产区采集黄麻炭疽病病原菌样本,分离纯化出92个菌株;rDNA-ITS区域的序列分析表明,其中11个为典型炭疽病病原菌。LSU区域的系统进化树和形态学特征鉴定显示,ZZ4、GX19等10个菌株为胶胞炭疽菌(Colletotrichumgloeosporioides),菌株CS3为黑线炭疽菌(Colletotrichum dematium)。人工接种的致病力测定表明,不同炭疽菌菌株致病力存在显著差异,其中胶胞炭疽菌菌株GX19致病力最强,表现为优势菌株。这些结果为黄麻炭疽病抗性基因位点挖掘和有效防治奠定了基础。     

Effect of high temperature on the production of 2n pollen grains in diploid roses and obtaining tetraploids via unilateral polyploidization

To integrate the gene pool of a wild species (primarily diploid) into a cultivated pool (primarily tetraploid), a crossing between a dihaploid cultivated rose and a hybrid of Rosa wichurana allowed to obtain interspecific diploid hybrids that produced 2n pollen grains. A return to a tetraploid level sought by breeders can then be considered using sexual polyploidization, obtained by crossing a tetraploid cultivated rose with these hybrids. Application of a high‐temperature regime led to a small but significant increase in the percentage of 2n pollen grains in these hybrids of up to 4.6%. This result was obtained by applying high temperatures close to 32°C during the day to plants cultivated in a glasshouse during recurrent cycles of bloom. Crosses were made between an unreleased tetraploid hybrid tea rose, as a female, and the diploid hybrid that produces the most 2n pollen grains. Tetraploid (42.1%) and triploid (57.9%) offspring were obtained. The use of these 2n pollen grains of the first division restitution type should facilitate the introgression of complex traits of interest.     

黄麻双生病毒CoYVV的分子鉴定和抗性种质筛选

越南黄麻黄脉病毒(Corchorus yellow vein Vietnam virus, CoYVV)是影响黄麻纤维品质和产量的双生病毒,其基因组含2个环状单链DNA(DNA-A和DNA-B)。鉴定黄麻双生病毒CoYVV并筛选抗病毒种质,不仅丰富对双生病毒分布和进化的认识,而且为黄麻抗性基因克隆奠定了基础。2018年福建省三明市福建农林大学洋中科教基地发现黄麻种质资源圃长果种黄麻福农5号疑似感染黄色花叶病。利用CTAB法提取该品种感病叶片DNA,通过PCR、滚环扩增及测序技术获得病毒基因组序列。通过同源序列比对和进化树构建明确该病毒与新旧世界双生病毒的关系。含有CoYVV DNA-A和CoYVV DNA-B侵染性克隆载体的农杆菌等比例混合,子叶注射法侵染具有代表性的7份长果种和7份圆果种黄麻品种(系),定期观察发病株数(病株率)并PCR检测接种黄麻的侵染率。PCR检测结果证实,福农5号病样感染了CoYVV,命名为CoYVV-FS。其DNA-A为2724 bp, DNA-B为2691 bp。进化分析表明,相较于旧世界菜豆金黄花叶病毒(begomoviruses), CoYVV-FS与新...     

基于黄麻转录组序列SNP位点的CAPS标记开发与验证

黄麻CAPS分子标记的开发,可以为黄麻遗传多样性分析、种质资源鉴定和分子标记辅助选择等研究提供有效方法。本试验以黄麻179和爱店野生种为材料,采用IlluminaHiSeq4000测序技术进行转录组测序,对其SNP位点进行分析,设计了与木质素合成基因4CL、COMT及转录因子MYB相兲的SNP引物,在此基础上,应用dCAPS Finder2.0软件开发了CAPS标记,幵对其有效性进行了验证。结果表明:(1)组装后的黄麻unigene序列共72,674条,序列总长度为29,705,997 bp,检测到的SNP位点总数为67,567个,平均每440 bp有1个SNP。(2)获得了39对分别与4CL、COMT和MYB相兲的SNP引物,从中筛选获得26对CAPS标记引物,开发成功率为66.7%,其中11对CAPS标记具有多态性,多态性比例为43.2%。(3)开发的CAPS标记能较好地将12份不同类型的黄麻种质区分开来,表明CAPS是适用于黄麻研究的较理想的分子标记方法,为黄麻遗传基础研究提供了可靠工具。     

Morphology and vigour of monohaploid potato clones,their corresponding homozygous diploids and tetraploids and their heterozygous diploid parent

Summary To study the joint effects of homozygotization and polyploidization in potato, the performance has been examined of five potato genotypes at three (x, 2x, 4x) and two genotypes at two (x, 2x) ploidy levels. Six out of the seven genotypes studied were compared with their heterozygous diploid parental clone. In this way comparisons could be made between i) the heterozygous diploid and its monohaploid derivatives, ii) three or two ploidy levels per genotye and iii) homozygous di- and tetreploids and their heterozygous diploid source.Large variation could be detected between monohaploids obtained from one diploid source. A striking increase in vigour was observed with somatic chromosome doubling from x to 2x, but less clearly from 2x to 4x. The relatively vigorous diploids showed a weaker response to tetraploidization than the less vigorous ones. The heterozygous diploid exceeded all homozygous di- and tetraploid derivatives in performance. The results of this study suggest positive gene dosage effects for tuber production more than for leaf area and plant height. The observations on plant vigour in homo- and heterozygotes suggest that dominance effects are stronger than additive gene effects. Owing to sterility problems, homozygous potato clones will presumably be of little importance for practical breeding.     

黄麻核心种质的遴选

遴选黄麻核心种质可为黄麻种质创新及新品种选育奠定基础。本研究以300份黄麻种质资源为基础,基于SSR分子标记和农艺性状考察,结合地理来源构建核心种质。结果表明,11个农艺性状变异系数变幅在13.06%～84.87%,表现出丰富的遗传多样性。按农艺性状聚类分析可划分为8个类群,按分子标记聚类可划分为10个类群。结合2个聚类分析、地理位置并按比例取样,建立一个由108份品种(系)组成的预选核心种质。采用44对SSR引物对其进行遗传差异分析,在遗传相似系数为0.65时,可把108份品种(系)分成圆果种和长果种两大类。根据遗传差异分析,剔除遗传相似系数大于或等于0.85的遗传冗余,获得84份品种(系)的核心种质,其中圆果种60份和长果种24份。比较84份核心种质与300份种质的农艺性状变异系数及Shannon-Wiener指数发现,两者之间相差不大,表明遴选的84份核心种质可以最大限度代表300份黄麻种质资源的遗传多样性加以利用和保存。     

In vitro induction of tetraploids in ornamental <Emphasis Type="Italic">Ranunculus</Emphasis>

This study investigates the capacity of the antimitotic agents colchicine, oryzalin and trifluralin for inducing polyploidisation of Ranunculus asiaticus ‘Alfa’ in vitro shoots. Flow cytometry was used to evaluate the optimal concentration of each antimitotic agent for polyploidisation. Trifluralin at a concentration of 2 μM resulted in the highest percentage of polyploidisation (27.5%), followed by a colchicine treatment of 200 μM, which induced 23.3% of polyploids. For oryzalin the highest percentage was achieved using a concentration of 1 μM. Different exposure periods were tested and turned out to be an important factor. The maximal exposure period tested (10 weeks) resulted in a significant increase in polyploidisation by oryzalin and trifluralin. In contrast, for colchicine (100 μM) exposure times of either 16 or 24 h did not significantly influence polyploidisation. Additionally the effect of the antimitotic agents on the viability was analysed. For colchicine no significant effect on the survival rate was observed, for trifluralin only a concentration of 10 μM affected viability whereas for oryzalin, concentration as well as exposure period were significant parameters. Flow cytometric data were confirmed by counting chromosomes in root tip cells.     

Amphidiploids between Cyclamen persicum Mill. and C. purpurascens Mill. induced by treating ovules with colchicine in vitro and sesquidiploids between the amphidiploid and the parental species induced by conventional crosses

Summary We cultured colchicine-treated hybrid ovules in vitro to produce fertile amphidiploids of C. persicum (2n=2x=48. referred to as AA) × C. purpurascens (2n=2x=34, referred to as BB). Seedlings and mature plants were obtained from the ovules without colchicine and those exposed to 50 mg/l colchicine for 5, 10 and 15 days, whereas they were not obtained from the ovules exposed to 50 mg/l colchicine for 20 days and 500 mg/l for 5, 10, 15 and 20 days. Although 8 mature hybrids derived from the ovules without colchicine produced a few fertile pollen grains, they failed to produce viable seeds by self-fertilization. The hybrids had 41 somatic chromosomes. Four and 3 mature plants were derived from ovules exposed to 50 mg/l colchicine for 10 and 15 days, respectively. One each among 4 and 3 mature plants showed a high frequency of pollen grain fertility, produced several seeds by self-fertilization, and had 82 somatic chromosomes which is twice the number of hybrid chromosomes (2n=41, AB). These findings indicated that these plants are amphidiploids (2n=82, AABB) between C. persicum and C. purpurascens. Three and 2 viable seeds were derived by the conventional crosses of diploid C. persicum × the amphidiploid and the amphidiploid × C. purpurascens, respectively. Flowering plants that developed from the seeds of diploid C. persicum × the amphidiploid were barely fertile and had 65 somatic chromosomes (2n=65, AAB), whereas those that developed from the seeds of the amphidiploid × C. purpurascens were barely fertile and had 58 somatic chromosomes (2n=58, ABB). The somatic chromosomes indicated that these plants are probably sesquidiploids between the amphidiploid and either C. persicum or C. purpurascens. The interspecific cross-breeding of cyclamen using the amphidiploids and the sesquidiploids is discussed.     

QTL identification for molecular breeding of fibre yield and fibre quality traits in jute

In jute (Corchorus olitorius), quantitative trait loci (QTL) analysis was conducted to study the genetics of eight fibre yield traits and two fibre quality traits. For this purpose, we used a mapping population consisting of 120 recombinant inbred lines (RILs) and also used a linkage map consisting of 36 SSR markers that was developed by us earlier (Das et al. 2011). The RIL population was derived from the cross JRO 524 (coarse fibre) × PPO4 (fine fibre) following single seed descent. Using single-locus analysis involving composite interval mapping, a total of 21 QTLs were identified for eight fibre yield traits whereas for fibre quality (fibre fineness), only one QTL was detected. The QTL for fibre fineness explained 8.31–10.56% of the phenotypic variation and was detected in two out of three environments. Using two-locus analysis involving QTLNetwork, as many as 11 M-QTLs were identified for seven fibre yield traits (excluding top diameter) and one M-QTL was identified for fibre fineness which accounted for 4.57% of the phenotypic variation. For six fibre yield traits, we detected 16 E-QTLs involved in nine QQ epistatic interactions. For fibre fineness, four E-QTLs involved in two QQ epistatic interactions and for fibre strength, six E-QTLs involved in three QQ epistatic interactions were identified. Eight out of the 11 M-QTLs observed for the fibre yield traits were also involved in QE interactions; for fibre fineness and fibre strength, no QE interactions were observed.     

Chromosome doubling of mature haploid Brussels sprout plants by colchicine treatment

Summary The effect of colchicine concentration, and the mode and time of colchicine application in doubling the chromosomes of haploid Brussels sprout plants was assessed by scoring treated plants for the presence of diploid flowers and seed set after self-pollination.When colchicine treatments were applied after the plants had been vernalised, using 2 dose rates and 3 methods of application, only 38.1% became doubled and only 13.8% produced seed. Treatment with 0.1% colchicine with or without the addition of 2% dimethyl sulphoxide gave doubling rates similar to those reached with 0.05% colchicine, but resulted in more damage to the apices.When 0.05% colchicine solution was injected into the plants' apices at varying times during vernalisation, the rate of doubling was 71.2% on average and 50.7% of plants gave seed on selfing.Overall doubling rates of plants where the apex was easily accessible were 79.0%, while for plants with dense terminal heads they were 35.0% and for plants with visible buds 31.4%.